Centrifugal Impeller and Centrifugal Blower

ABSTRACT

A centrifugal impeller includes a cover, a base opposite the cover and a plurality of blades. The cover has an inlet. The plurality of blades surround the inlet and are arranged between and connect the cover and the base. Inlet edges of one end of the blades adjacent the center of the impeller define a cavity in communicate with the inlet. The dimension of the cavity gradually decreases along the direction from the cover towards the base.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C.§119(a) from Patent Application No. 201310452740.4 filed in The People'sRepublic of China on Sep. 29, 2013.

FIELD OF THE INVENTION

This invention relates to a blower and in particular, to a centrifugalblower and a centrifugal impeller especially suitable for thecentrifugal blower.

BACKGROUND OF THE INVENTION

A centrifugal blower includes a motor and a centrifugal impeller. Thecentrifugal impeller includes a cover, a base and a plurality of bladeswhich are arranged between the cover and the base and connect the coverand the base. The cover has an inlet for entrance of air flow. Ends ofthe blades adjacent the center of the impeller define a cavity facingthe inlet of the cover.

The centrifugal impeller is driven by the motor. A low pressure zone isformed at the center of the impeller. Air outside the blower enters intothe cavity via the inlet of the impeller, then flows into the flowpassages formed by the blades and is eventually discharged from theimpeller.

One of the disadvantages of the current design is that the efficiency ofthe blower is low.

SUMMARY OF THE INVENTION

Accordingly, in one aspect thereof, the present invention provides acentrifugal blower comprising an electric motor and a centrifugalimpeller driven by the motor, the centrifugal impeller comprising: acover, a base opposite the cover and a plurality of blades, the coverhaving an inlet, the plurality of blades surrounding the inlet andarranged between and connecting the cover and the base, inlet edges ofends of the blades adjacent the center of the impeller defining a cavityin communication with the inlet, wherein the dimension of the cavitygradually decreases in the direction from the cover towards the base.

Preferably, each inlet edge forms an angle γ with the base in the rangeof 55° to 75°. Ideally, angle γ is in the range of 62° to 70°. Mostpreferably, angle γ is in the range of 65° to 68°.

Preferably, each blade comprises first and second arc segments whichhave different radii, the first arc segment being located at a radiallyinner portion of the blade, and the second arc segment being located ata radially outer portion of the blade.

Preferably, the radius of the second arc segment is greater than theradius of the first arc segment.

Preferably, the blower further comprises a diffuser and a casing mountedto the diffuser, the diffuser being mounted to the motor and disposedbetween the motor and the impeller, the impeller being received in achamber defined by the diffuser and the casing, the casing having anopening facing the inlet of the impeller.

Preferably, the diffuser has a plurality of guide holes and a pluralityof smoothly curved diffusing passages each extending from an outer endto an inner end, the air flow generated by the impeller flowing from oneside of the diffuser adjacent the impeller to the side of the diffuseradjacent the motor via the guide holes, outer ends of the diffusingpassages being in communication with corresponding guide holes and innerends of the diffusing passages being in communication with one another.

Preferably, the diffuser has a plurality of passage walls forming thediffusing passages, one end of at least one of the passage wallsadjacent the center of the diffuser has a guide portion for guiding theair flow in adjacent diffusing passages to two sides of a mountingportion connecting the diffuser to the motor.

Preferably, the image of the guide portion in the radial section of themotor is raindrop-shaped.

Preferably, ends of two of the passage walls of the diffuser adjacentthe center of the diffuser has two streamlined guide portions which arediametrically opposite to each other.

Preferably, the motor includes a stator comprising a stator core andstator windings wound about teeth of the stator core, and the two guideportions are respectively located at gaps between the stator windings soas to guide the air flow in the diffusing passages to the statorwindings.

Preferably, the diffuser has an end wall and a side wall extending fromthe end wall towards the motor, the passage walls and the diffusingpassages being formed inside a space defined by the end wall and theside wall, axial ends of the stator windings extending into the hollowspace and located at two sides of the guide portions.

Preferably, the side wall has a plurality of inclined guide slopes, theguide holes being located at the ends of the guide slopes.

Preferably, each of the guide portions has a mounting hole for receivinga fastener for fixing the diffuser to the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way ofexample only, with reference to figures of the accompanying drawings. Inthe figures, identical structures, elements or parts that appear in morethan one figure are generally labeled with a same reference numeral inall the figures in which they appear. Dimensions of components andfeatures shown in the figures are generally chosen for convenience andclarity of presentation and are not necessarily shown to scale. Thefigures are listed below.

FIG. 1 illustrates a blower in accordance with a preferred embodiment ofthe present invention;

FIG. 2 shows the blower of FIG. 1, with a casing removed;

FIG. 3 shows a centrifugal impeller being a part of the blower of FIG.1;

FIG. 4 is a partial view of a part of the impeller of FIG. 3;

FIG. 5 is a view of the impeller of FIG. 3, with a cover removed;

FIG. 6 is a plan view of the impeller of FIG. 3, with the cover removed;

FIG. 7 is a view of an impeller side of a diffuser, being a part of theblower of FIG. 1;

FIG. 8 is a view of a motor side of the diffuser of FIG. 7;

FIG. 9 is a plan view of the motor side of the diffuser of FIG. 7;

FIG. 10 is a plan view of the diffuser and motor parts superimposed; and

FIG. 11 shows the blower of FIG. 1 viewed from another angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a centrifugal blower 20 in accordance with apreferred embodiment of the present invention comprises an electricmotor, a centrifugal impeller 23 mounted to a shaft of a rotor of themotor, a diffuser 31 mounted to the motor and arranged between the motorand the impeller 23, and a casing 21 mounted to the diffuser 31. Theimpeller 23 is received in a chamber 22 defined by the diffuser 31 andthe casing 21. The casing 21 has an opening 19 facing an inlet of theimpeller 23.

In the embodiment, the motor is a universal motor. A stator of the motorcomprises a stator core 41, stator windings 44 wound about teeth of thestator core 41, an end cap 43 mounted to the stator core 41, and a brushassembly 45 mounted to the end cap 43. In this embodiment, the diffuser31 functions as another end cap of the motor. The diffuser 31 and endcap 43 are mounted to the axial ends of the stator core 41. The diffuser31 has two projected mounting portions 38 which bear against the statorcore 41. The rotor of the motor comprises a shaft, a commutator 51 fixedto the shaft, a rotor core and rotor windings (not shown in thefigures). The shaft is mounted to the end cap 43 and the diffuser 31 viabearings such that the rotor may rotate relative to the stator.

The diameter of the diffuser 31 is slightly greater than that of theimpeller 23. A plurality of guide holes 34 a adjacent outlets of theimpeller 23 are formed at the outer periphery of the diffuser 31. Airflowing out from the outlets of the impeller 23 flows from the impellerside of the diffuser 31 to the motor side of the diffuser 31 the guideholes 34 a.

Referring to FIGS. 3 and 4, the impeller 23 comprises a cover 25, a base24 opposite the cover 25, and a plurality of blades 26. The cover 25 hasan inlet 27 formed at a center thereof and facing the opening 19 of thecasing 21. The plurality of blades 26 surrounding the inlet are disposedbetween and connect the cover 25 and the base 24. Ends of the blades 26adjacent the center of the impeller 23 form a cavity 28 in communicationwith the inlet of the impeller 23. An inlet edge 26 e of the inner endof each blade 26 adjacent the center of the impeller is inclinedrelative to the base 24 of the impeller 23. Therefore, the dimension ofthe cavity gradually decreases along the direction from the cover 25 tothe base 24. By this configuration, when the impeller 23 rotates, theair flows into the cavity and then into the flow passages formed by theblades 26. The amount of air in the cavity gradually decreases along thedirection towards the base 24. As the change of the amount of air in thecavity matches the change of the dimension of the cavity, the air flowis more stable and uniform.

The inlet edge 26 e of each blade 26 forms an angle θ with the normalline L1 of the base 24 and forms an angle γ with the end surface of thebase 24. The line L2 in the figure represents the imaging direction ofthe inlet edge 26 e on the base 24. As the normal line L1 of the base isperpendicular to the line L2, the sum of the angle θ and the angle γequals 90°. Experiments show that the impeller 23 has good performanceand high efficiency when the angle γ is in the range of 55° to 75° andthe angle 0 is accordingly in the range of 35° to 15°.

Preferably, the angle γ is in the range of 62° to 70° and the angle θ isaccordingly in the range of 28° to 20°.

More preferably, the angle γ is in the range of 65° to 68° and the angleθ is accordingly in the range of 25° to 22°.

Referring to FIGS. 5 and 6, each blade 26 includes a first arc segment26 a and a second arc segment 26 b which have different radii. The firstarc segment 26 a is located at the radially inner end of the blade 26adjacent the center of the impeller 23 and the second arc segment 26 bis located at the radially outer end of the blade 26 away from thecenter of the impeller 23. Compared with the traditional blade with asingle arc segment, the blades 26 in the present invention have betterperformance and higher efficiency.

In the embodiment, the radius R2 of the second arc segment 26 b isgreater than the radius R1 of the first arc segment 26 a.

Referring to FIGS. 7 and 8, the diffuser 16 has an end wall 32 and anannular side wall 29 extending from the end wall 32 towards the motor.The end wall 32 and the side wall 29 form a hollow space 30 facing themotor. A bearing for supporting the shaft of the rotor of the motor ismounted in a recess at the center of the end wall 32. The side wall 29has crimping recesses 35 facing the motor. During the assembly, portionsof the casing 21 is crimped into the recesses 35 (see FIG. 1). The sidewall further has a plurality of guide slopes 33 inclined from the endsurface of the end wall 32 towards the motor and a plurality of guideholes 34 at the end of the guide slopes 33. Referring back to FIGS. 1and 2, the end wall 32 of the diffuser 31 is adjacent to the base 24 ofthe impeller 23. The guide slopes 33 and the guide holes 34 a areadjacent to the outlets of the impeller 23. Air flowing out from theoutlets of the impeller 23 flows into the guide holes 34 a under theguidance of the guide slopes 33.

Referring to FIGS. 8 and 9, a plurality of smoothly curved diffusingpassages 34 having outer ends and inner ends are formed in the hollowspace of the diffuser 31. The outer ends of the diffusing passages 34are in communication with corresponding guide holes 34 a and the innerends of the diffusing passages 34 are in communication with one another.Therefore, air flow from the impeller 23 is able to flow from theimpeller side of the diffuser 31 to the motor side of the diffuser 31via the guide holes 34 a, then flows into the center of the diffuser 31via the diffusing passages 34, and passes through the motor in the axialdirection to cool the motor.

The diffuser 31 has a plurality of passage walls 36 at the side adjacentthe motor to form the diffusing passages 34. Ends of the passage walls36 adjacent the center of the impeller are spaced from one another anddefine a space at the center of the diffuser 31. The end of at least oneof the passage walls 36 has a streamlined guide portion 38 a for guidingthe air flow in adjacent diffusing passages 34 to two sides of the guideportions 38 a. Preferably, the image of the guide portion 38 a in theradial cross-section of the motor is raindrop-shaped.

Referring to FIGS. 8 to 11, in this embodiment, two guide portions 38 aare arranged at two mounting portions 38 of the diffuser 31. The twomounting portions 38 are respectively arranged at the ends of twopassage walls 36 adjacent the center of the diffuser 31. The two guideportions 38 are opposite to each other about the center of the diffuser31. Axial end surfaces of the guide portions 38 a have a mounting recess39 for fastening to the stator core 41 of the motor. The stator of themotor includes a stator core 41 and two stator windings wound aboutteeth of the stator core 41. Axial ends of the two stator windingsextend into the cavity of the diffuser 31 and are located at two sidesof the guide portions 38 a in the circumferential direction. The twoguide portions 38 a are circumferentially arranged between the twostator windings 44 for guiding the air flow in the diffusing passages 34to the stator windings 44. The air flow is thus concentrated on twosides of a virtual line connecting the two guide portions 38 a so as tobetter cool the stator windings 44. The guide portions 38 a areraindrop-shaped, which can reduce the resistance of the air flow.

Further, the two guide portions 38 a have mounting holes 37 for mountingthe diffuser to the motor. In the embodiment, the mounting holes 37 arelocated in the mounting recesses 39. During assembly, bolts or screws 60pass through the mounting holes of the mounting recess 39 and the statorcore 41 to connect with the end cap 43 so as to fix the diffuser 31, thestator core 41 and the end cap 43 together.

In the description and claims of the present application, each of theverbs “comprise”, “include”, “contain” and “have”, and variationsthereof, are used in an inclusive sense, to specify the presence of thestated item but not to exclude the presence of additional items.

Although the invention is described with reference to one or morepreferred embodiments, it should be appreciated by those skilled in theart that various modifications are possible. Therefore, the scope of theinvention is to be determined by reference to the claims that follow.

1. A centrifugal blower comprising an electric motor and a centrifugalimpeller driven by the motor, the centrifugal impeller comprising: acover, a base opposite the cover and a plurality of blades, the coverhaving an inlet, the plurality of blades surrounding the inlet andarranged between and connecting the cover and the base, inlet edges ofends of the blades adjacent the center of the impeller defining a cavityin communication with the inlet, wherein the dimension of the cavitygradually decreases in the direction from the cover towards the base. 2.The blower of claim 1, wherein each inlet edge forms an angle γ with thebase in the range of 55° to 75°.
 3. The blower of claim 1, wherein eachinlet edge forms an angle γ with the base in the range of 62° to 70°. 4.The blower of claim 1, wherein each inlet edge forms an angle γ with thebase in the range of 65° to 68°.
 5. The blower of claim 1, wherein eachblade comprises first and second arc segments which have differentradii, the first arc segment being located at a radially inner portionof the blade, and the second arc segment being located at a radiallyouter portion of the blade.
 6. The impeller of claim 5, wherein theradius of the second arc segment is greater than the radius of the firstarc segment.
 7. The blower of claim 1, further comprises a diffuser anda casing mounted to the diffuser, the diffuser being mounted to themotor and disposed between the motor and the impeller, the impellerbeing received in a chamber defined by the diffuser and the casing, thecasing having an opening facing the inlet of the impeller.
 8. The blowerof claim 7, wherein the diffuser has a plurality of guide holes and aplurality of smoothly curved diffusing passages each extending from anouter end to an inner end, the air flow generated by the impellerflowing from one side of the diffuser adjacent the impeller to the sideof the diffuser adjacent the motor via the guide holes, outer ends ofthe diffusing passages being in communication with corresponding guideholes and inner ends of the diffusing passages being in communicationwith one another.
 9. The blower of claim 8, wherein the diffuser has aplurality of passage walls forming the diffusing passages, one end of atleast one of the passage walls adjacent the center of the diffuser has aguide portion for guiding the air flow in adjacent diffusing passages totwo sides of a mounting portion connecting the diffuser to the motor.10. The blower of claim 9, wherein the image of the guide portion in theradial section of the motor is raindrop-shaped.
 11. The blower of claim9, wherein ends of two of the passage walls of the diffuser adjacent thecenter of the diffuser has two streamlined guide portions which arediametrically opposite to each other.
 12. The blower of claim 11,wherein the motor includes a stator comprising a stator core and statorwindings wound about teeth of the stator core, and the two guideportions are respectively located at gaps between the stator windings soas to guide the air flow in the diffusing passages to the statorwindings.
 13. The blower of claim 12, wherein the diffuser has an endwall and a side wall extending from the end wall towards the motor, thepassage walls and the diffusing passages being formed inside a spacedefined by the end wall and the side wall, axial ends of the statorwindings extending into the hollow space and located at two sides of theguide portions.
 14. The blower of claim 13, wherein the side wall has aplurality of inclined guide slopes, the guide holes being located at theends of the guide slopes.
 15. The blower of claim 11, wherein each ofthe guide portions has a mounting hole for receiving a fastener forfixing the diffuser to the motor.